Receptor-mediated gene transfer is appealing because the vectors are noninfectious, it is nontoxic in vivo, and gene delivery is specific to receptor-bearing cells. Expression of reporter genes and therapeutic genes is often high-level, but transient. However, targeting the asialoglycoprotein receptor with compacted DNA-protein complexes can lead to protracted gene expression in some animals. What determines the level and duration of gene expression is unknown. When the serpin- enzyme-complex receptor (sec-R) on human hepatoma cell lines (such as HepG2 or HuH7) is targeted, changes in the protein portion of the complex result in marked changes in intensity and duration of transgene expression. Because ligand, polycation, and DNA can each be labeled separately and followed within the target cell, the cell biologic basis for protracted high level gene expression can be investigated. Protein configurations which produce different intensity and duration of gene expression will be compared with respect to intracellular trafficking. In addition, pharmacologic probes will be used to identify rate-limiting steps. Finally, the ability of these different complexes to mediate reporter gene delivery in rats in vivo will be tested. The tissue distribution of transgene expression and toxicity will be determined. Because sec-R is abundant on hepatocytes, an important target cell for gene therapy of many metabolic diseases, such as ornithine transcarbamylase deficiency or 1-antitrypsin deficiency, and on neurons which accumulate -amyloid in Alzheimer's disease, as well as macrophages which are the site of accumulated material in some storage diseases, delivery of genes to these cells via sec-R has therapeutic potential. Even if therapy proves an elusive goal, the potential is great for understanding the cell biologic basis of high-level long term expression of genes in plasmid vectors delivered by receptor-mediated endocytosis.